Cargo Ships Emit Twice as Much Soot as Previously Thought: NOAA Study

Usually when we talk about transportation emissions causing climate change here at TreeHugger, we focus on CO2 emissions or methane emissions—the usual suspects in the global warming discussion. In regards to cargo shipping, companies are investigating how much slowing down ships can reduce emissions. A new study conducted by the National Oceanic and Atmospheric Administration and the University of Colorado shows, however, that it’s not just the carbon emissions from cargo shipping which are a serious global warming concern, but also the soot these ships produce.

The findings of the study were published in Geophysical Research Letters, but Science Daily gives us the layman’s translation:Cargo Shipping Worse Than Thought, Tugboats the WorstGlobally commercial shipping releases 130,000 tonnes of soot annually—a figure which is expected to increase by 2-6% annually as global shipping expands. By volume the worst offenders are tugboats, which emit nearly a gram of soot be kilogram of fuel burned. In contrast, tankers and container ships emit about half a gram of soot per kilogram of fuel: Twice as much as previously thought.

In ports and along coastlines this soot can have serious affects on human health, causing tens of thousands of premature deaths each year due its contribution to air pollution. However, the study predicts that additional climate change in the Arctic could occur because of soot emissions.

Why Soot Matters to Climate Change The small carbon particles that make up soot trap 30% as much heat as carbon dioxide and has an affect on how clouds form, produce rain, and alter the heat balance of a region. As the Arctic warms from other factors, and commercial shipping lanes potentially open up, the soot from cargo ships (assuming nothing is done to reduce this soot) will hasten the melting taking place in the region. Furthering melting will occur, making the shipping lanes viable for longer each year, et cetera, et cetera.

What I take away from this study is that, as one of my TreeHugger colleagues put it: There is no free trade, from the standpoint of the environment, when you’re talking about how our current transport system is fueled.